Base station for supporting communication rate modifications

ABSTRACT

A base station which prevents the transmission of data between communicating nodes until the data communication rate required by the communicating nodes has been established selectively suppresses the confirmation tone that a receiving node sends to an originating node. The transmission of voice, facsimile or modem data is prevented until the communication path has been established at the desired communication rate. This permits the base station to reliably transport encoded data at a plurality of data rates without precise synchronization.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of application Ser. No.09/354,042, filed Jul. 15, 1999, which is a continuation of applicationSer. No. 08/671,067, filed Jun. 27, 1996 now U.S. Pat. No. 5,953,346,issued Sep. 14, 1999 which application(s) are incorporated herein byreference.

BACKGROUND

[0002] 1. Field of the Invention

[0003] This invention generally relates to wireless communicationsystems. More particularly, the invention relates to a wireless digitalCDMA communication system that selectively adjusts the data transmissionrate depending upon the bandwidth required by the communication withoutthe loss of data during the transmission rate adjustment.

[0004] 2. Description of Related Art

[0005] The telecommunications industry has recently experienced stronggrowth in the use of wireless technology including cellular, satelliteand microwave communications. As the popularity and use of wirelesscommunication systems has increased, the finite bandwidth allocated toeach type of wireless communication has become increasingly valuable.Since it is unlikely that additional bandwidth to support user growthwill be allocated for existing applications, many of the recent advancesin telecommunication hardware and software have been directed towardincreasing the transmission rate of data while utilizing the same or adecreased bandwidth.

[0006] One of the problems associated with wireless communication ofdata is that many different types of communicating nodes are currentlyin use including computers, facsimile machines, automatic calling andanswering equipment and other types of data networks. These nodes may beable to communicate at a plurality of different data rates and must beproperly synchronized to avoid losing data during the establishment ormaintenance of a communication.

[0007] The establishment and synchronization of communications iscurrently performed using a variety of different techniques. Forexample, the system disclosed in U.S. Pat. No. 4,384,307 (Kuzmik et al.)includes a communication adapter for interfacing a transceiver to acommunication line. The system requires bit level manipulation of datato properly synchronize two communicating nodes. Reformatting of datausing this technique is computationally expensive and prone to errors.

[0008] Another type of system is disclosed in U.S. Pat. No. 4,583,124(Tsuji et al.) which permits two nodes to quickly establishsynchronization at a desired communication speed by storing informationconcerning each communicating node in memory. However, requiring anoriginating node to store information about each receiving node isimpractical given today's communication environment.

[0009] Accordingly, there is a need for a simple and effective techniquefor switching the data transmission rate of a communication network tothe required rate while preserving the integrity of the data transmittedbetween two communicating nodes.

SUMMARY

[0010] The present invention is a CDMA communication system whichprevents the transmission of data between communicating nodes until thedata communication rate required by the communicating nodes has beencompletely established throughout the system. The system selectivelysuppresses the confirmation tone that a receiving node sends to anoriginating node. Accordingly, the transmission of voice, facsimile ormodem data is prevented until the communication path has beenestablished at the desired communication rate. This permits the systemto reliably transport encoded data at a plurality of data rates across atelecommunication system which may lack precise synchronization.

[0011] Accordingly, it is an object of the present invention to providea system and method for reliably transmitting encoded data by preventingcommunication of data until the communication system has achieved thedata transmission rate required by communicating nodes.

[0012] Other objects and advantages of the present invention will becomeapparent after reading the description of a presently preferredembodiment.

BRIEF DESCRIPTION OF THE DRAWING(S)

[0013]FIG. 1 is a schematic overview of a code division multiple accesscommunication system in accordance with the present invention;

[0014]FIG. 2 is a block diagram of the communication system of FIG. 1connected to originating and terminating nodes;

[0015]FIG. 3 is a flow diagram of the establishment of a communicationchannel between originating and terminating nodes in accordance with theprior art;

[0016]FIG. 4 is a flow diagram of the establishment of a communicationchannel between originating and terminating nodes in accordance with thepresent invention; and

[0017]FIG. 5 is a block diagram of a base station in accordance with theteachings of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0018] The preferred embodiment will be described with reference to thedrawing figures where identical numerals represent similar elementsthroughout.

[0019] A communication network 10 embodying the present invention isshown in FIG. 1. The communication network 10 generally comprises one ormore base stations 14, each of which is in wireless communication with aplurality of subscriber units 16, which may be fixed or mobile. Eachsubscriber unit 16 communicates with either the closest base station 14or the base station 14 which provides the strongest communicationsignal. The base stations 14 also communicate with a base stationcontroller 20 which coordinates communications among the base stations14. The communication network 10 may also be connected to a publicswitched telephone network (PSTN) 22, wherein the base stationcontroller 20 also coordinates communications between the base stations14 and the PSTN 22. Preferably, each base station 14 communicates withthe base station controller 20 over a wireless link. Although the linkbetween the base stations 14 and the base station controller 20 is shownas a wireless link, it should be apparent to those skilled in the artthat a land line between the base stations 14 and the base stationcontroller 20 may be provided. This is particularly applicable when abase station 14 is in close proximity to the base station controller 20.

[0020] The base station controller 20 performs several functions.Primarily, the base station controller 20 provides all of the overhead,administrative and maintenance (OA&M) signaling associated withestablishing and maintaining all of wireless communications between thesubscriber units 16, the base stations 14, and the base stationcontroller 20. The base station controller 20 also provides an interfacebetween the wireless communication system 10 and the PSTN 22. Thisinterface includes multiplexing and demultiplexing of a plurality ofcommunication signals that enter and leave the system 10 via the basestation controller 20. Although the wireless communication system 10 isshown employing antennas to transmit RF signals, one skilled in the artwill recognize that communications may be accomplished by microwavesatellite uplinks.

[0021] Referring to FIG. 2, the communication system 10 is generallyconnected to originating nodes 40 and terminating nodes 44. In order toconserve as much bandwidth as possible, the communication system 10selectively allots the bandwidth required for supporting the datatransmission rate required by the originating and terminating nodes 40,44. In this manner, the system 10 ensures that the bandwidth is utilizedefficiently. Voiced communications may be effectively transmitted acrossa 32 Kb/s adaptive pulse code modulation (ADPCM) channel. However, ahigh speed fax or data modem signal requires at least a 64 Kb/s pulsecode modulation (PCM) signal to reliably transmit the communication.Many other types of modulation techniques and data transmission ratesmay also be utilized by originating and terminating nodes 40, 44. Thesystem 10 must be able to effectively allocate bandwidth and dynamicallyswitch between these data communication rates and modulation schemes ondemand.

[0022] The communication system 10 provides a communication link betweenthe originating and terminating nodes 40, 44. The originating andterminating nodes 40, 44 may comprise computers, facsimile machines,automatic calling and answering equipment, data networks or anycombination of this equipment. For robust communication of data it isimperative to ensure that the communication system 10 switches to thedata transmission rate required by the communicating nodes 40, 44 priorto the transmission of any data.

[0023] Referring to FIG. 3, the typical procedure for establishingcommunications between originating nodes 40 and terminating nodes 44 isshown. The originating node 40 periodically transmits a calling tone(step 100) which indicates that a data communication, (not a voicecommunication), is to be transmitted. The calling tone which is sentfrom the originating node 40 to the terminating node 44 is detected bythe terminating node 44 (step 102) which initiates several actions.First, the terminating node 44 prepares to send a data communication(step 104). Next, the terminating node 44 transmits an answering tone(step 106) to the originating node 40 to confirm that the terminatingnode 44 has received the calling tone. Upon receipt of the answeringtone (step 108), the originating node 40 begins the transmission of data(step 110), which is received by the terminating node 44 (step 112).With the communication link established at the data transmission rate,the originating and terminating 40, 44 nodes transmit and receive datauntil termination of the communication.

[0024] One problem with this process is that the transmission rate ofthe communication system 10 is transparent to both the originating andterminating nodes 40, 44. Modification of the transmission rate from alow rate (that supports voice communication) to a high rate (thatsupports encoded data communication) ensures that data will be reliablyand quickly transmitted over a communication channel. However, the newtransmission rate must be completely established throughout thecommunication system 10 to prevent false interpretation of tonestransmitted by the originating node 40. The originating node 40 maybegin transmission of data at a high rate before the system 10 has fullyswitched from 32 Kb/s ADPCM to 64 Kb/s PCM resulting in loss of data.

[0025] In order to obviate tone misinterpretation and to prevent theresulting erroneous operation of the originating or terminating nodes40, 44, the present invention blocks the transmission of the confirmingtone to the originating node 40 until the new data transmission rate hasbeen completely established throughout the communication system 10. Thisprevents the reception of the answering tone at the originating node 40and ensures the reliable transportation of encoded data at a higher rateacross a communication system 10 which lacks the precise synchronizationwhich would otherwise be required.

[0026] The operation of the system 10 of the present invention will beexplained with reference to FIG. 4. The communication system 10facilitates communications between an originating node 40 and aterminating node 44. As shown, the actions of the originating node 40(steps 202, 212 and 214) and the actions of the terminating node 44(steps 206, 207, 208 and 218) are the same as in FIG. 3. The operationof the communication system 10 is transparent to both the originatingnode 40 and the terminating node 44.

[0027] In operation, the originating node 40 periodically transmits acalling tone (step 202) which indicates a data communication. Thecommunication system 10 performs several actions in response to receiptof the calling tone (step 204). First, the calling tone is received at32 Kb/s ADPCM which is the standard communication setting for voicecommunications. The system 10 detects the calling tone and initiates aswitch to 64 Kb/s PCM in order to handle the high-speed datatransmission. This switch must be implemented by the base station 14,the subscriber unit 16 and the base station controller 20. Although thesystem 10 immediately begins the switching over to the new datatransmission rate, the process takes approximately 1500 msec toimplement. Accordingly, the system 10 transmits the calling tone to theterminating node 44 at 32 Kb/s ADPCM.

[0028] The terminating node 44 detects the calling tone (step 206) andprepares to send a data communication (step 207). The terminating node44 subsequently transmits the answering tone (step 208) which, whenreceived by the originating node, will cause the originating node 40 tobegin transmission of data.

[0029] The communication system 10 receives the answering tone from theterminating node 44. However, the system 10 does not forward theanswering tone to the originating node 40 until the switch to 64 Kb/sPCM has been established throughout the system 10. After the system 10has confirmed that the switch to 64 Kb/s PCM has been achieved, itpermits the answering tone to pass through to the originating node 40,which receives the tone (step 212). In response to the answering tone,the originating node 40 begins transmission of data (step 214). Thesystem 10 receives the data and begins transmission of data at the newdata transmission rate (64 Kb/s PCM) (step 216) to the terminating node44 which receives the data (step 218). Since the communication channelhas been established, the originating and terminating nodes 40, 44continue to communicate over the system 10 in this manner (steps 214,216 and 218) until the communication is terminated.

[0030] Referring to FIG. 5, a more detailed block diagram of the basestation controller 20 is shown. The base station controller 20 controlsat least a portion of the communication link between two communicatingnodes 40, 44. This link comprises the transmission path 300 from a firstcommunicating node to the base station controller 20, the transmissionpath 302 within the base station controller 20, and the transmissionpath 304 from the base station controller 20 to the second communicatingnode. The transmission paths 300, 304 to and from the base stationcontroller 20 may include a plurality of base stations 14 and subscriberunits 16 which are controlled by the base station controller 20.

[0031] It should be appreciated by those of skill in the art that theestablishment of a communication channel between communicating nodes 40,44 is a complex procedure involving a plurality of tasks performed bythe base station 14, the subscriber unit 16 and the base stationcontroller 20. A detailed description of the entire procedure is outsidethe scope of the present invention. Accordingly, only those portions ofthe procedure for establishment of a communication channel relevant tothe present invention will be described hereinafter.

[0032] The communications between an originating node 40 and aterminating node 44 are transmitted over a virtual channel as is wellknown by those of skill in the art. Since the entire spectrum is used bythe CDMA communication system 10, communications from the originatingnode 40 to the terminating node 44 are transmitted over the samefrequency band as communications from the terminating node 44 to theoriginating node 40. After the virtual channel has been established, theoriginating and terminating nodes 40, 44 may freely communicate.

[0033] The base station controller 20 includes a calling tone detector310, a microprocessor 312 and an answering tone blocker 314. The callingtone detector 310 monitors the communication channel which has beenestablished in order to detect the calling tone. When a calling tone istransmitted from an originating node 40, the calling tone detector 310detects the calling tone, which causes the base station controller 20 toinitiate the switch to a higher data transmission rate. Themicroprocessor 312 subsequently informs any other base stations 14 orsubscriber units 16 through which the communication is to be routed(hereinafter called communicating equipment) to initiate the switch tothe higher data transmission rate.

[0034] The microprocessor 312 activates the answering tone blocker 314which will prevent the answering tone from being transmitted through thesystem 10. Each piece of communicating equipment 14, 16, 20 transmits anacknowledgment to the microprocessor 312 of the base station controller20 when the higher data transmission rate has been achieved. Themicroprocessor 312 subsequently deactivates the answering tone blocker314 which permits the answering tone to be forwarded to the originatingnode 40. The communicating nodes 40, 44 commence data transmission overthe communication system 10 at the higher data transmission rate.

[0035] Although the invention has been described in part by makingdetailed reference to the preferred embodiment, such detail is intendedto be instructive rather than restrictive. For example, the functionsperformed by the base station controller 20 shown in FIG. 5 may, in analternative embodiment, be performed by a base station 14 coupled witheither the originating or terminating nodes 40. The functions of a basestation 14 may also be combined with the base station controller 20, toform a master base station. Additionally, different data rates andmodulation schemes may be employed. It will be appreciated by thoseskilled in the art that many variations may be made in the structure andmode of operation without departing from the spirit and scope of theinvention as disclosed in the teachings herein.

What is claimed is:
 1. A base station including an apparatus forsuppressing selective communications during communication ratemodification, the base station coupled between first and said secondcommunicating nodes, the base station including: means for establishinga communication channel between said first and said second nodes at afirst data rate; means for detecting a transmission from said first nodeon said channel; means for determining whether said transmissionrequires a change in data rates to a second data rate; switch means,responsive to said determining means, for switching said communicationchannel to said second data rate; and blocking means, responsive to saiddetermining means, for blocking transmissions from said second nodeuntil said second data rate has been established.
 2. The base station ofclaim 1 wherein said detecting means detects tones at a plurality ofselective frequencies and said tones initiate a change to said seconddata rate.
 3. The base station of claim 2 wherein said switch meansswitches said first data rate to said second data rate, which is higherthan said first data rate.
 4. The base station of claim 3 wherein saidfirst data rate is 32 kb/s and said second data rate is 64 kb/s.
 5. Thebase station of claim 4 wherein said first data rate employs pulse codemodulation and said second data rate employs adaptive pulse codemodulation.
 6. The base station of claim 1 wherein said switch means isresponsive to said determining means to switch said established channelto one of a plurality of alternative channels, depending upon a datarate and modulation type required by said transmission.
 7. A basestation for facilitating wireless communications between an originatingnode and a terminating node, the base station located such that at leasta portion of the communication between said originating node and saidterminating node passes through the base station, the base stationselectively adjusting transmission rates without the loss of data duringthe transmission rate adjustment, the base station including: means forestablishing a communication channel between said originating node andsaid terminating node, said channel comprising a first communicationpath from said originating node to said terminating node and a secondcommunication path from said terminating node to said originating node;means for monitoring said first communication path for a signal, saidsignal indicating the request for a transmission rate adjustment;adjustment means, responsive to said monitoring means, for adjusting thetransmission rate of said communication channel; and suppression means,responsive to said detection means, for suppressing communications onsaid second communication path until the desired transmission rate isestablished.
 8. The base station of claim 7 wherein said monitoringmeans detects signals having selective frequencies indicating a requestfor an increased transmission rate.
 9. The base station of claim 7wherein said adjustment means switches said communication channel to asecond communication channel having a higher transmission rate.
 10. Thebase station of claim 9 wherein said communication channel has atransmission rate of 32 kb/s and said second communication channel has atransmission rate of 64 kb/s.
 11. The base station of claim 9 whereinsaid communication channel uses pulse code modulation and said secondcommunication channel uses adaptive pulse code modulation.
 12. The basestation of claim 7 wherein said signal indicates a transmission rate anda modulation type required and said adjustment means is responsive tosaid monitoring means to switch said channel to one of a plurality ofalternative channels, depending upon a transmission rate and amodulation type required by said signal.
 13. A wireless base station,interposed between a first communicating node and a second communicatingnode, the base station for suppressing selective communications duringchannel modification, the base station comprising: means forestablishing a first duplex communication channel between said firstnode and said second node comprising a transmit (Tx) portion and areceive (Rx) portion; said channel having a first communication rate andmodulation type; means for detecting a transmission from said first nodeon said Tx portion; means for determining whether said transmissionrequires a change to a second duplex communication channel having asecond communication rate and modulation type; switch means, responsiveto said determining means, for switching said first communicationchannel to said second communication channel; and blocking means,responsive to said determining means, for blocking transmissions on saidRx portion until said second communication channel is established. 14.The system of claim 13 wherein said detecting means detects selectivetransmitted frequencies on said Tx portion which indicate a requirementfor a change to said second communication channel.
 15. The base stationof claim 13 wherein said second communication channel has a fastercommunication rate than said first communication rate.
 16. The basestation of claim 13 wherein said first communication rate is 32 kb/s andsaid second communication rate is 64 kb/s.
 17. The base station of claim13 wherein said first communication channel uses pulse code modulationand said second communication channel uses adaptive pulse codemodulation.
 18. The base station of claim 13 wherein said switch meansis responsive to said determining means to switch said establishedchannel to one of a plurality of alternative channels, depending upon acommunication rate and a modulation type required by said transmission.19. A wireless base station for facilitating communications between afirst communicating entity and a second communicating entity, the basestation selectively suppressing communications during bearer ratemodification, the base station comprising: means for establishing acommunication channel between said first entity and said second entity;means for detecting a transmission from said first entity over saidchannel; determining means responsive to said detecting means,determining if a new communication channel is required; switch means,responsive to said determining means, for switching over saidcommunication channel to said new communication channel; and blockingmeans, responsive to said determining means, for blocking transmissionsfrom said second entity to said first entity until said switchover iscompleted.
 20. A base station capable of modifying its communicationrate, the base station handling at least a portion of a communicationbetween an originating node and a terminating node, the base stationcomprising: a receiver for receiving a first communication from saidoriginating node at a first communication rate; a detector for detectinga request for a modification of said communication rate; ratemodification means for modifying said first communication rate to saidrequested communication rate; a transmitter for transmitting said firstcommunication at said first communication rate to said terminating node;whereby said receiver receives an answering tone from said terminatingnode; said rate modification means includes a suppressor for suppressingsaid answering tone until said modification is completed; and saidtransmitter transmits said answering tone to said originating node.